OzoneSherrif - Don't give away Vader, Yoda, or the twins. Trying to come up with ways to work within the confines of the given story is part of the fun.
If you really want to start from scratch, this is the only info that the OT gives you as a starting point (sorry if this is too wordy):
What are Jedi Knights:
For a thousand generations the Jedi Knights were the guardians of peace and justice in the Old Republic, before the dark times, before the Empire. Jedi Knights must have the deepest commitment and the most serious minds. They do not crave adventure and excitement. A young Jedi named Darth Vader, a pupil of Kenobi, was seduced by the dark side of the force and helped the Empire hunt down and destroy the Jedi Knights.
What is a lightsaber:
The lightsaber is the weapon of the Jedi Knights. It is not as clumsy of random as a blaster. It is a civilized weapon of a more civilized day.
What is the Force:
The Jedi Knights get their power from “The Force” which is an energy field created by all living things. It surrounds us and penetrates us. It binds the galaxy together. A Jedi can feel the force flowing through him and between all living things. They must be at peace and passive and only use “The Force” for knowledge and defense. Jedi can feel disturbances in “The Force,” They can also sense each other and contact each other through “The Force” as well as see other places and times. It can also have a strong influence on the weak-minded. By the time of the original trilogy “The Force” is considered an ancient and even hokey religion with sorcerer’s ways by some and a form of well-wishing or blessing to others.
Who is Ben Kenobi:
Kenobi was trained by a Jedi Master named Yoda. He was reckless (at least in his estimation) in his youth. He served Leia’s adopted father in the Clone Wars as a general. Anakin is already a great pilot when they meet, but Kenobi is amazed at how strongly the force was with Anakin. He thought he could instruct Anakin as well as Yoda. He was wrong.
Who is Anakin:
Anakin was a Jedi Knight. His brother Owen thought he should have stayed home and not gotten involved, but he followed Obi wan on “some damn-fool idealistic crusade.” He was “the best star pilot in the galaxy, a cunning warrior and a good friend." He wants his son to someday have his lightsaber.
Who is the Emperor:
The Emperor seduces Anakin to the Dark Side. The Dark Path is not stronger, but it is quicker and easier. When you feel the force, but cannot control it, is when you are tempted. Anger, fear, hate and aggression lead to the Dark Side. The name Anakin has no meaning to Vader. The Emperor knew that if Anakin had any offspring they would be a threat to him. He ends up dissolving the entire Republic.
Who are Anakin’s children:
Luke is raised on Tatooine, the planet the farthest from the bright center of the galaxy, by his aunt and uncle. He maintains his father’s true name and does not remember his mother and for some reason finds Dagobah familiar. Leia’s adopted home, Alderaan, is a peaceful planet with no weapons. She knows she was adopted and remember just images and feelings of her real mother. She remembers her as beautiful and kind but sad.
Everything else is pretty much wide open for ideas.